Notes, summaries, assignments, exams, and problems for Biology

Prenatal development is divided into two main periods: the embryonic period, which occurs during the first 2 months, and the fetal period, which follows. The embryonic period begins in the oviduct with the segmentation of the zygote. This involves successive mitotic divisions that produce 2 cells, called blastomeres, approximately 36 hours after fertilization. These cells then divide into 4, then 8, then 16, and so on, forming a morula.

About 5 days after fertilization, the morula transforms into a hollow, spherical structure called the blastocyst. The blastocyst consists of a cavity and two sets of cells: trophoblast cells (or the outer cell mass) and the embryoblast (the inner cell mass). After 7 days, the trophoblast attaches to the endometrium... Continue reading "Prenatal Development: Embryonic and Fetal Stages" »

Desenvolvemento Embrionario Inicial

Implantación e Primeiras Etapas

A implantación no endometrio ocorre de forma temperá. Unha vez implantado, o embrión continúa crecendo e desenvolvéndose.

Formación do Sistema Nervioso e Órganos

Prodúcese a formación inicial do sistema nervioso. Arredor dos tres meses, o embrión convértese nun feto e os seus órganos comezan a funcionar.

Reprodución Humana Asistida: Técnicas

Inseminación Artificial

A inseminación artificial consiste en introducir artificialmente o esperma no tracto reprodutor feminino.

Fecundación In Vitro (FIV)

A fecundación in vitro (FIV) consiste en fecundar o óvulo co esperma fóra do corpo, no laboratorio. O termo in vitro fai referencia ao uso de material de laboratorio, como... Continue reading "Embrións, Reprodución Asistida e Células Nai" »

The Digestive System

Role of Digestion

During the process of digestion, food is broken down. The broken molecules can then be used by cells.

Digestive Tract Structure

The digestive tract is a duct, a 9-meter long pipe through which food passes, extending from the mouth to the anus.

Glands: Glands pour their juices into the tube. The main glands are the salivary glands, liver, and pancreas.

Food is transported by a wave of contraction and relaxation called peristaltic movements.

Layers of the Digestive System

Internal or Mucosal Layer: This layer secretes digestive juices and mucus, protecting the surface. Nutrients are absorbed through this layer.

Muscularis: This layer consists of involuntary muscle fibers that contract. The anal sphincter muscles... Continue reading "How Your Body Processes Food and Air" »

Endocrine System

The endocrine system is formed by cells and glands that secrete specific hormones. These hormones are effective messengers that regulate various bodily functions through feedback mechanisms.

Endocrine Glands

Pituitary Gland

Anterior Lobe

• GH (Somatotropin)
• ACTH (Adrenocorticotropin)
• TSH (Thyroid Stimulating Hormone)
• PRL (Prolactin)
• FSH (Follicle-Stimulating Hormone)
• LH (Luteinizing Hormone)

Posterior Lobe

• Vasopressin (ADH - Antidiuretic Hormone)
• Oxytocin

Hypothalamus

The hypothalamus controls the neurohypophysis through nerve fibers and releases or inhibits pituitary factors.

Adrenal Glands

Cortex

• Glucocorticoids: Regulate carbohydrate and protein metabolism and inhibit the immune response.
  • Cortisol
  • Corticosterone
• Mineralocorticoids: Regulate Na-

Puberty: Hormonal Changes

Boys: Sperm production, increased bone thickness and muscle mass, voice deepening, beard growth, and the appearance of pubic and axillary hair.

Girls: First menstruation, breast growth, widened hips, and the appearance of pubic and axillary hair.

Female Reproductive System

Ovaries, Fallopian tubes, uterus, vagina, clitoris, labia majora, and labia minora.

Male Reproductive System

Testes, prostate, urethra, epididymis, vas deferens, seminal vesicles, penis, and scrotum.

Key Definitions in Human Development

• Embryo: The second phase of zygote development occurs when it attaches to the endometrium.
• Fetus: The third stage of embryonic development, starting in the second trimester.
• Nidation: The moment when the zygote attaches to

Muscular System

Muscle Characteristics

Involuntary. Located in the heart. Striated fibers are present inside longitudinal filaments called myofibrils. Muscle cells are made of two proteins: actin and myosin. Some form rhabdomyosarcoma.

Types of Muscles

• Long or Fusiform: (spindle-shaped)
• Flat or Planar: (e.g., diaphragm)
• Orbicular: (round body, e.g., orbicularis oculi)

Tendons join muscles to bones. Two muscles are involved in any movement: agonist (contracts) and antagonist (relaxes).

Skeletal System

3.2 - Bones

Functions

• Support the body and give it shape.
• Allow movement of various body parts.
• Protect internal organs (brain, lungs, etc.).
• Serve as the main repository of minerals (calcium, potassium, etc.).
• Some bones act as organs of blood cell production.

Understanding Human Body Systems

The Locomotor System

The locomotor system allows humans and animals to move and interact with their environment. It consists of the bony system and the muscular system.

The Skeletal System

Components and Functions

The skeletal system includes the human skeleton and its components:

• Bones: Provide internal support. Muscles are attached to bones via tendons.
• Articular Cartilage: Cartilage linking different pieces of bone.

Joints

Structure and Movement

Joints are the junction of skeletal bones and allow a wide range of body movements.

Joint Conditions

Common conditions affecting joints include:

• Dislocation: When a bone is out of the joint.
• Sprain: Injury to the ligaments when joints are stressed.
• Arthritis: An inflammation of

Common Illnesses and Their Causes

Illnesses Caused by Viruses

Viruses are responsible for a variety of illnesses, some of which are highly contagious. Here are a few examples:

• The Common Cold: A highly contagious illness that causes mild discomfort, increased nasal secretions, congestion, and sneezing. It typically does not cause fever. Transmission occurs through direct contact, but the virus can also spread through the air. Frequent handwashing is crucial for prevention.
• Flu (Influenza): Often confused with the common cold due to its prevalence in winter and similar transmission methods. However, the flu generally causes greater discomfort, including joint pain, and is a more serious illness.
• AIDS (Acquired Immunodeficiency Syndrome): A serious

Cellular Functions

Cellular functions are basic units of life and conduct nutrition, relationships, and reproduction. Unicellular cells perform all these functions within a single cell, while multicellular organisms have specialized cells.

• Nutrition: Molecular intake from the external environment provides energy to renew cellular structures. This process inside the cell is known as metabolism.
• Relationships: Cells communicate with the outside environment, adapting to changes and maintaining stability.
• Reproduction: New cells are formed from existing ones. In unicellular organisms, this leads to a new being. In multicellular organisms, it replaces dying cells and increases cell numbers during growth. Cells pass their genetic material to their daughter

Item 14. Physical Agents: Thermal Environment

Introduction

Thermal environment refers to environmental conditions including:

• Temperature
• Humidity
• Physical activity

Homeotherms

Homeotherms maintain internal temperature within very narrow ranges.

• Danger: Heat stress
• Heat discomfort
• Comfort
• Discomfort from cold
• Danger: Hypothermia

Thermal Equilibrium

Thermal equilibrium between body and environment involves mechanisms of thermoregulation.

Mechanisms of Thermoregulation

Q = M ± R ± C - E

• Q: Heat generated or heat buildup
• M: Metabolic activity
• R: Radiation exchange
• C: Exchange by convection
• E: Heat lost by evaporation

Radiation Exchange (R)

Heat exchange that originates between two solid bodies in proximity.

Exchange by Convection (C)

Mechanism by which the body exchanges... Continue reading "Thermal Environment: Effects, Regulation, and Comfort" »